# yaml-language-server: $schema=../../../../schema/control.schema.json
id: CB-UBU-SVC-008
title: Disable web server services on systems that do not serve web content
finding:
  title: A web server can run on a system that does not serve web content
  description: A forgotten web server publishes default pages, modules and files that nobody maintains.
status: active
profiles: [core]
risk:
  severity: medium
assessment: automated
tags: [services, http, attack-surface]

description: |
  Web servers packaged by Ubuntu: Apache (`apache2.service`), nginx (`nginx.service`) and
  lighttpd (`lighttpd.service`). They are often pulled in as dependencies of other software.

  The control passes when each unit is masked or not installed at all.
rationale: |
  A web server that nobody expects is not patched, monitored or hardened, and may publish
  directories or status pages that reveal information. It is remotely reachable code.
impact: |
  Masking a unit stops it and prevents it from starting again. **Web servers and reverse proxies
  must exclude this control in their tailoring file**, with the reason, for example:

  ```yaml
  exclude:
    - control: CB-UBU-SVC-008
      reason: Web server role (nginx serves the intranet).
  ```
notes: |
  A unit that does not exist counts as compliant, so removing the package is an equally valid fix.

audit:
  manual: |
    For each unit, run `systemctl is-enabled <unit>`. It must print `masked`, or fail because the
    unit does not exist: `apache2.service`, `nginx.service`, `lighttpd.service`.
  logic: all
  checks:
    - id: apache2
      engine: systemd-unit
      description: Apache HTTP server.
      spec: { unit: apache2.service, state: masked }
    - id: nginx
      engine: systemd-unit
      description: nginx web server.
      spec: { unit: nginx.service, state: masked }
    - id: lighttpd
      engine: systemd-unit
      description: lighttpd web server.
      spec: { unit: lighttpd.service, state: masked }

remediation:
  manual: |
    Stop and mask each unit that is installed: `systemctl mask --now <unit>`. If the package is not
    needed at all, remove it instead: `apt purge apache2 nginx lighttpd`.
  effects:
    restart: none
    disruption: low
    lockout_risk: false
  rollback: |
    Run `systemctl unmask <unit>` then `systemctl enable --now <unit>`.
  scripts:
    - id: apache2
      from_check: apache2
    - id: nginx
      from_check: nginx
    - id: lighttpd
      from_check: lighttpd

references:
  - title: apache2(8), Ubuntu manual pages
    url: https://manpages.ubuntu.com/manpages/noble/man8/apache2.8.html
    publisher: Canonical
    kind: vendor-doc
    accessed: 2026-10-19
  - title: nginx(8), Ubuntu manual pages
    url: https://manpages.ubuntu.com/manpages/noble/man8/nginx.8.html
    publisher: Canonical
    kind: vendor-doc
    accessed: 2026-10-19
  - title: systemctl(1), Ubuntu manual pages
    url: https://manpages.ubuntu.com/manpages/noble/man1/systemctl.1.html
    publisher: Canonical
    kind: vendor-doc
    accessed: 2026-10-19
  - title: ANSSI-BP-028 v2.0 - Recommandations de configuration d'un système GNU/Linux (R62)
    url: https://messervices.cyber.gouv.fr/documents-guides/fr_np_linux_configuration-v2.0.pdf
    publisher: ANSSI
    kind: guide
    accessed: 2026-10-19
mappings:
  - framework: anssi-linux
    framework_version: "2.0"
    id: R62
    relation: partial
    note: R62 asks to disable every unneeded service; this control covers web servers.
  - framework: nist-800-53r5
    framework_version: "5.1.1"
    id: CM-7
    relation: partial
  - framework: cis-ubuntu-2004
    framework_version: "3.0.0"
    id: "2.1.18"
    relation: equivalent
  - framework: cis-ubuntu-2204
    framework_version: "3.0.0"
    id: "2.1.18"
    relation: equivalent
  - framework: cis-ubuntu-2404
    framework_version: "2.0.0"
    id: "2.1.6"
    relation: equivalent
  - framework: cis-ubuntu-2604
    framework_version: "1.0.0"
    id: "2.1.19"
    relation: equivalent
threats:
  - framework: mitre-attack
    id: T1190
related_controls:
  - id: CB-UBU-SVC-009
    type: related

authors:
  - name: Alice
    github: Sn0wAlice
verified:
  - date: 2026-10-19
    by: Sn0wAlice
    versions: ["20.04"]
    environment: Proxmox VM, Ubuntu 20.04 cloud image, kernel 5.4.0-216-generic
    notes: "Stock image passes (units absent); with apache2 installed the check fails, server-hardened remediation masks the units, audit passes, unchanged on a second run and after reboot."
  - date: 2026-10-19
    by: Sn0wAlice
    versions: ["22.04"]
    environment: Proxmox VM, Ubuntu 22.04 cloud image, kernel 5.15.0-198-generic
    notes: "Stock image passes (units absent); with apache2 installed the check fails, server-hardened remediation masks the units, audit passes, unchanged on a second run and after reboot."
  - date: 2026-10-19
    by: Sn0wAlice
    versions: ["24.04"]
    environment: Proxmox VM, Ubuntu 24.04 cloud image, kernel 6.8.0-147-generic
    notes: "Stock image passes (units absent); with apache2 installed the check fails, server-hardened remediation masks the units, audit passes, unchanged on a second run and after reboot."
  - date: 2026-10-19
    by: Sn0wAlice
    versions: ["26.04"]
    environment: Proxmox VM, Ubuntu 26.04 cloud image, kernel 7.0.0-38-generic
    notes: "Stock image passes (units absent); with apache2 installed the check fails, server-hardened remediation masks the units, audit passes, unchanged on a second run and after reboot."
introduced_in: 0.1.0
created: 2026-10-19
updated: 2026-10-19